SU1308316A1 - Apparatus for measuring arterial blood pressure - Google Patents

Abstract

The invention relates to medical technology. The purpose of the invention is to ensure the reliability of measurement through light outerwear. The device comprises a cuff 1, a source 2 of overpressure and a sensor 3 of pressure in the cuff. The first 6 and second 7 differentiators are connected in series. The input of the third differentiator 13 is connected to the output of the amplifier 4 through the filter 8 and the first increment determination unit 14, the output of which is connected to the control input of the first memory block 9. A second block for determining increments 15 is connected between the output of the second differentiator 7 and the control input of the second memory block 10. The information inputs of the first and second memory blocks 9 and 10 are connected to the output of the analog-digital converter 5, and their outputs are connected to the outputs of the display 12 and the display I. The half-wave detector 16 serves to cut off the positive part of the pulse oscillation signal and can be performed based on opamp. 1 h. item f-ly, 2 ill. I (L co o oo Sla O5

Description

The invention relates to medical technology and can be used to diagnose the state of the cardiovascular system.

The aim of the invention is to ensure the accuracy of the measurement through lightweight outerwear.

FIG. 1 is a diagram of an apparatus for measuring blood pressure; in fig. 2 are diagrams explaining the process of measuring blood pressure parameters.

The device contains a pneumatically connected compression cuff 1, an overpressure source 2 with a decompression speed controller and a cuff pressure sensor 3 to which amplifier 4 and analog-to-digital converter 5 are connected in series, the first 6 and second 7 differentiators in series, filter 8, the first 9 and the second 10 memory blocks, the systolic pressure display 11 and the diastolic pressure display 12, the third differentiator 13, the input of which is connected to the output of the amplifier 4 through the filter 8 and the first block 14 o the increments, the output of which is connected to the control input of the first memory block 9, the second increment determination block 15 connected between the output of the second differentiator 7 and the control input of the second memory block 10 and the detector 16 connected between the output of the filter 8 and the input of the first differentiator 6, wherein the information inputs of the first and second memory blocks 9 and 10 are connected to the output of the analog-digital converter 5, and their outputs to the outputs of the diastolic pressure display 12 and the systolic pressure display 11.

The first increment determination unit 14 (the second unit 15 is assembled according to the same scheme and operates identically) contains a comparator 17, the first input and output of which are respectively the input and output of the block 14 as a whole, element 2I, the first input 18 of which is connected to the output of the comparator 17 the second input is connected to the clock generator 19, and the output is to the counting input of binary counter 20, the digital-to-analog converter 21, the digital inputs of which are connected to the discharge outputs of the counter 20, and the analog output to the second input of the comparator 17, and the first input of the counter 20 is connected to the common point of resistor 22 and capacitor 23, the other terminal of which is connected respectively to power the mud. The increment determination unit 14 is made on the basis of a known analog-to-digital converter circuit with a one-time setting of the counter to zero for the entire pressure measurement cycle. A string consisting of a capacitor 23 and a resistor 22 is used for initial setup

ki of the counter 20 after switching on the power supply and for prohibiting its operation for the time of charging the capacitor 23 through the resistor 22. This delay is necessary due to the presence of

transients in the device nodes when power is turned on.

The device contains a pneumatically connected compression cuff 1, an overpressure source 2 in the form of a rubber duct with a valve and a decompression speed controller, and a semiconductor bridge strain gauge 3. These nodes are typical, can be designed in a known manner and serve to create a smooth cuff pressure reduction mode and converting the instantaneous pressure value to a proportional voltage. The output voltage of the sensor is amplified by amplifier 4 by approximately 30 dB.

This signal, shown in FIG. 2,

diagram a, is a slowly falling pressure in cuff 1, modulated in amplitude by pulse oscillations of the artery under the cuff, therefore it is necessary to ensure the bandwidth

sensor 3 and amplifier 4 from a constant component to a frequency of about 15 Hz. With an amplifier output, a bandpass filter B is associated with a passband of 0.5 to 15 Hz and a gain in the passband of about 20 dB. To the rectangle of his

there are no special requirements; a second order filter on the operational amplifier can be used in practice. Such a filter provides satisfactory suppression of the constant component, noise, pickup.

and fast artifacts that lie outside its bandwidth, and the fulfillment of its functional purpose — extracting the signal of pulse artery oscillations under the cuff. Next, the selected signal goes to the differentiator 13, which forms the first information signal (Fig. 2, diagram c), the first derivative of the pulse oscillations, and the serial circuit containing the one-period detector 16 and two differentiators 6 and 7, which forms the second the information signal (Fig. 2, diagram d) is the second derivative of the dicrotic depressions of the pulse oscillations. The full-wave detector 16 serves to cut off the positive part of the pulse oscillation signal and can be made on the basis of an operational amplifier. The dycrotic (negative) valleys of the pulse oscillations are twice differentiated in differentiators 6 and 7. All. Three differentiators of the device are made on the basis of an operational amplifier, a capacitor and a resistor. It is necessary to ensure in them a phase shift equal to 90 ° in the whole

frequency band, and compensation for some loss of signal level. Next, the generated first and second information signals are fed to the corresponding increment determination units 14 and 15, in which the amplitude amplitudes of the information signals are analyzed at the rate of the occurrence of the pulse oscillations.

Measurements are carried out as follows. Preliminarily, a patient's limb area (e.g., a shoulder) is applied with a compression cuff 1. With the help of an overpressure source 2 of the cuff, the pressure is first raised to a value that obviously exceeds the patient’s estimated systolic blood pressure, and then with a decompression rate regulator, a gradual reduction mode is set. cuff pressure. After this, a measurement cycle is started. In this case, a signal is received from the pressure sensor 3, which is pneumatically connected to the cuff 1, which is the sum of the signal proportional to the pressure in the cuff, and the signal of the pulse oscillations of the artery under the cuff, and is amplified in amplifier 4. This signal, shown in FIG. . 2, diagram a, is fed to an analog-to-digital converter 5, which continuously measures it and, in digital form, provides information about the current pressure in the cuff to memory blocks 9 and 10.

In addition, the signal from amplifier 4 is fed to a bandpass filter 8, which cuts off the constant component, noise, pickups and fast artifacts lying outside its passband, which extracts the pulse artery oscillation signal from the cuff from the recorded total signal under the cuff and amplifies it. Then, from this signal shown in FIG. 2, diagram b, form two information signals: the signal of the first derivative of the pulse oscillations (Fig. 2, diagram c) by means of a differentiator 13 and the signal of the second derivative of the dicrotic depressions of the pulse oscillations (Fig. 2, diagram e) by a pulse oscillation detector 16 and subsequent double differentiation in differentiators 6 and 7. For comparison, in FIG. 2, the diagram w shows the signal of the second derivative of the pulse oscillations without preliminary detection. Further, in the formed information signals, the characteristic features — the moments of the maxima (point A in Fig. 2, diagram g and point B in Fig. 2, diagram m. C) are detected. At these times, a signal is recorded that is proportional to the pressure in the compression cuff. The systolic blood pressure Rsmt corresponds to point A, diastolic blood pressure

0

Rdnlst. - point B (Fig. 2, diagram and). This operation is carried out using increment determination blocks 14 and 15, which control the operation of memory blocks 9 and 10. The information contained in the memory blocks is indicated on displays X and 12. Comparator 17 compares the levels of input voltages and controls pa6oToii of element 2 и 18. The latter is closed by a logical “0, as long as the voltage at the first input of the comparator is 17 M ng1e, than the voltage at its second input. In this case, the pulses from the clock generator 19 operating in the continuous mode M. do not pass to the counting input of the binary counter 20. During positive information oscillation of the information signal, the voltage at the first input of the comparator 17 exceeds the voltage at its second input. The comparator 17 generates a logical "1, the element 18 opens and the counter code 20 begins to increase.

0 The voltage at the output of the digital-to-analog converter 21 increases along a stepped curve up to the moment when its value exceeds the voltage value at the first input of the comparator 17, i.e.

5, the operation time of the comparator 17. Logic element 18 is closed with a logical " O, and counter code 20 corresponds to the oscillation amplitude of the information signal.

Since the counter 20 is then not set to zero, the amplitude code of this oscillation is stored in its memory even after the voltage decreases at the first input of the comparator 17, i.e., after the oscillation decays, and increases even when oscillators appear information signal with

 larger amplitude.

An increase in counter code 20 is proportional to the difference in amplitudes of this and previous oscillations. In this case, the comparator 17 generates a control pulse indicating that there is an increment in the pulse of the information signal. This incremental control pulse from the output of the increment determination unit 14 is supplied to the 9th unit of data block, which is a random access memory made on the basis of a parallel register with recording information on the front of the control pulse. The information inputs of both memory blocks 9 and 10 are connected in parallel and connected to the digital outputs of the analog-to-digital converter 5. Since the input signal is the output signal of amplifier 4 (Fig. 2, diagram a), the digital information at the output of converter 5 presented in the code, in any MONICHT time corresponds to a slowly falling off. have pressure cuff. Consequently, the information recorded in memory blocks 9 and 10, also cooTBTCTBN eT pressure in man5

The moment of occurrence of increments of positive oscillation amplitudes of information signals. Displays 12 and 11 are connected to the digital outputs of memory blocks 9 and 10 to continuously display the current digital information recorded in memory blocks 9 and 10, respectively. Three-digit LED or liquid crystal indicators can be used as displays.

Claims (2)

1. A device for measuring blood pressure, blood, containing an overpressure source connected to a compression cuff and a pressure sensor, the output of which through an amplifier and analog-to-digital converter is connected to two memory blocks, the outputs of which are connected to displays, and two serially connected differentiator, characterized in that, in order to ensure the reliability of the measurement through a light upper clothes, it has a serially connected filter, a third differentiator and the first increment definition block, the output of which is connected to the second input the first memory block, the detector connected to the output of the filter and through the first and second successively connected differentiators to the second increment determination block, the output of which is connected to the second memory block, and the input of the filter connected to the output of the amplifier. 2. The device according to claim 1, characterized in that the first and second increment determination units are made in series of a comparator, element 2I, a counter and a digital-analog converter, the output of which is connected to the second input of the comparator, the second input of element 2I is connected to the output of a clock generator and the second counter input is connected to a resistor-capacitor circuit with a power source, the first comparator input being the input and the output of the comparator being the output of the increment determination unit. t memory ycmpoucmia FIG. Z iriftw